X-rays have been used for inspection purpose for many years especially for the ability to detect impurities with higher density than the substance under test. Despite efforts to focus the x-rays from the generator and confine them to the product item under test and the sensor, x-rays tend to scatter whenever they collide with matter, therefore, in the work environment, workers must be protected from harmful effects of exposure to extraneous x-ray radiation.
In the field of endeavor of the present invention where the product item is typically packaged food and drink items such as bottled liquids moving along a conveyor, it is customary to fully surround the generator, product item under test, sensor and the associated portion of the conveyor with an enclosure constructed with x-ray shielding material, typically of UMW (ultra high molecular weight) to avoided excessive thickness requirements.
In one approach of known practice, the enclosure is configured with a pair of tunnels, one at the entry opening and the other at the exit opening, dimensioned to fit closely around the product containers moving along the conveyor; if the product containers are close-spaced, they tend to fill these tunnels sufficiently to prevent excessive x-ray radiation from escaping through the entry and exit tunnel openings. However in the event that a sizeable gap occurs somehow between the product containers along the conveyor, the increase in x-ray radiation escaping through the tunnels may become excessive and potentially harmful.